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There are measured acute toxicity data available for octane on fish (Morrow et al. 1975). However, due to significant methodological deficiencies this investigation is considered not realiable. Therefore, an LL50 (96 h) was calculated using the Petrotox computer model (v. 3.04), which combines a partitioning model used to calculate the aqueous concentration of hydrocarbon components as a function of substance loading with the Target Lipid Model used to calculate acute and chronic toxicity of non-polar narcotic chemicals. Petrotox computes toxicity based on the summation of the aqueous-phase concentrations of hydrocarbon block(s) that represent a hydrocarbon substance and membrane-water partitioning coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated freshwater fish 96-h LL50 (Lethal Loading Rate) value is 2.587 mg/L. Also the chronic toxicity was estimated with this model, resulting in a 28-day NOELR (No Observed Effect Loading Rate) value of 0.579 mg/L.

There are measured acute toxicity data available for octane on five different species of freshwater and marine aquatic invertebrate species (Adema & van den Bos Bakker 1987, Bobra et al. 1983, Donkin et al. 1989, Abernethy et al. 1986). The data provided by Adema & van den Bos Bakker (1987) are considered most realiable and a test conducted with Daphnia is chosen as key study. The acute toxicity, as measured by immobilisation of Daphnia and mortality to Chaetogammarus and Mysidopsis, was evaluated in fresh- and saltwater by using water accomodated fractions (WAFs). Octane produced acute toxicity to Daphnia, Chaetogammarus and Mysidopsis at 0.66 mg/L. Measured data on chronic toxicity are read-across to hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics based on a category approach. A study of the chronic toxicity, as measured by survival, sublethal effects, reproduction, and length of first generation adults, conducted with Daphnia using WAFs (Wilbury Laboratories 2004) resulted in a NOELR of 1 mg/L.

As regards toxicity to algae measured data are available but not considered reliable (Brooks et al. 1977). Thus, an EL50 (72 h) and a NOELR (72 h) were calculated using the Petrotox computer model (v. 3.04). The estimated freshwater algae 72-h EL50 (Effect Loading Rate) and NOELR (No Observed Effect Loading Rate) values are 2.084 and 0.466 mg/L, respectively, based on biomass. With the same model toxicity to microorganisms were calculated. The estimated protozoan, Tetrahymena pyriformis, 48-hr EL50 value is 10.86 mg/L based on growth inhibition.